By the way, phisics is phisics. For some mysterious reason, my personal experience agrees 100% with phisics, Starboard test team's does not.
Over time I used quite a few medium wind slalom boards of about 100 lts. volume; and lighter meant nicer to use (I am a recreational sailor with a taste for speed, so nice to use means a good deal to me), always but in one single case where I went too far (5.3 kg, Nomex construction).

Light weight means low inertia and the boards' ability to follow the water surface with less sticking in and (unwanted) taking off. In my view and experience this is an advantage until one is able to rule and tame the board's ride. A pro rider, plenty heavy strong and fit, will love light weight to a much farther extent than a recreational sailor, whose legs and ankles will be fatigued pretty soon and loose the ability to keep the board on track. So for recreational sailors "lighter is better" is not 100% true, but rather there is an "optimum" point of balance. That point, in my view, for medium wind slalom boards of about 100 lts. (what I ride) falls somewhere between 5.5 and 6.0 kg, which is lower than Starboard's offerings (iS94 and iS101) in that class, even not considering the +/-6% tolerance that in my experience hopelessly reads "+" for people buying their kit in shop.
Well one could say 6.2 is not that far from 6.0; but 6.2 + some% is very far from 5.5!

For this reason, I thought the intoduction of carbon wood versions was the occasion for Starboard to introduce lighter slalom boards; and for this reasons those "corporate" answers "trust me, I tested it and despite everything this is what we found" sound fake to me. Maybe I am wrong but, honestly, this all drives me another step back from entering that shop and order an iSonic. Was I able to sort a really "-6%" sample from the production lot, it could be different.

By the way. Ola: there is no way vertical accelleration induced by chop may soak energy from forward motion: the directions of that accelleration and that motion are 90° from each other. It is true that extra weight will make the board react slower because of inertia, so there will be more "sticking in" before lift will free the hull from a piece of chop, and more "air time" from any piece of chop before one is able to push the board down and apply drive again.